The present invention generally relates to an apparatus for removing sub-micron to micron-sized metallic particles from circulating fluids and, in particular, is concerned with a magnetic assembly for use on a disposable canister-type filter that attracts and holds ferro-metallic particles and prevents circulation of these particles in an engine or other mechanical device which circulates fluids for lubrication, cooling, etc.
Most engines used in automobiles, trucks, and boats include canister-type oil filters that filter the engine's lubricating oil, removing foreign matter therefrom. To eliminate the larger particles of foreign matter, the engine oil is typically forced through a porous material in the oil filter that allows the liquid oil to pass through, but does not allow the passage of the larger particles. In this manner, the larger particles of foreign matter can be removed from the engine's lubricating oil. However, because this separation technique relies upon filtration through a porous material, particles that are smaller than the openings in the porous material are normally not removed by the filter medium. One particularly harmful type of foreign matter which accumulates in lubricating oil is the small metallic particles which can be created by frictional contact between the moving metal parts of the engine. These metallic contaminants are known to damage important engine components as they circulate through the engine.
Small metallic particles often have a cross-sectional dimension smaller than the openings in the porous filter material. When not removed by the oil filter, these small metallic particles will freely circulate through the engine until they are finally removed when the oil is changed. Typically, the porous material used in oil filters consists of a fibrous material that has openings as small as an average of 20 microns in diameter. Hence, metallic particles with a cross-sectional dimension of 20 microns or smaller are often not trapped by the filter.
These micron and sub-micron-sized metallic particles are a major cause of wear for the moving components of the engine. Specifically, as the oil is circulated throughout the engine to lubricate the various moving components, the metallic particles entrained in the oil are carried to the interface between the moving components. At these locations, metal bears against metal, and reliance is placed solely upon the oil to maintain a lubricating film. Damage to the adjoining surfaces is likely when the metal particle contaminants are introduced to such critical interfaces. This damage eventually results in a degradation of the close tolerances between the moving parts, causing the performance of the engine to decrease accordingly. By some estimates, these metallic particles are the cause of more than one-half of the wear on the engine.
One approach taken by the prior art to eliminate these particles has been to install a magnetized drain plug in the crankcase of the engine. The magnetized drain plug generates a magnetic field around the magnet within the crankcase, which in turn attracts and removes some of the metallic particles from the lubricating oil as it flows through the crankcase. However, when the engine is running, the flow of oil through the crankcase can be at such a high flowrate so as to carry the metallic particles entirely through the magnetic field produced by the magnetized drain plug. In other cases, the magnetic field itself is insufficiently strong or extensive to attract and remove a meaningful number of particles from the lubricating oil.
Another prior approach to solve this problem has been to attach a magnet to the oil filter to create a magnetic field within the filter that attracts and holds the metallic particles against the walls of the filter, thereby preventing circulation of the metallic particles in the engine. An example of this approach is shown in U.S. Pat. No. 5,078,871 issued Jan. 7, 1992, to McCready. It is intended that these magnets create a magnetic field within the oil filter attracting the particles to the inner surface of the outer oil filter wall where the magnet assembly is attached.
Unfortunately, the device disclosed in U.S. Pat. No. 5,078,871 and other such known devices attached to the filter are unlikely to generate a sufficiently strong magnetic field to attract most it not all of the metallic particles in the oil. Metallic particles contained in the oil even if they pass through the weak magnetic field are not likely to be attracted and thus they continue to circulate through the engine. Furthermore, the filter strip disclosed by U.S. Pat. No. 5,078,871 is permanently affixed to the outside of the oil filter. Hence, the effective life of the device is only as long as the effective life of the filter, and once the oil filter is disposed of, the permanently affixed magnetized strip is also thrown away.
Prior solutions to the problem of micron and sub-micron sized metallic particles in a circulating fluid are disclosed in co-pending patent application Ser. No. 08/268,828, filed Jun. 30, 1994, and hereby incorporated by reference. The invention of that application comprises a magnetic member having a plurality of alternating regions of polarity affixed to the interior or exterior of the metal canister of the oil filter. A steel flux amplifier band covers the outer surface of the magnetic member to amplify and direct the magnetic field within the oil filter. As the oil passes through the filter, the magnetic field generated by the magnet on the canister is sufficiently strong to attract and retain the metallic particles as a result of the flux amplifier band.
However, other configurations for a magnetic member could advantageously provide a sufficiently strong magnetic field to attract and retain the metallic particles.
Consequently, a need still exists for an improved device for removing micron and sub-micron-sized metallic particles from the lubricating oil flowing through an engine. To this end, there is a need for a device that can generate a stronger magnetic field, and with a greater depth of field, than any of the devices previously known heretofore in the art. This device should be mountable on the oil filter and adaptable for use on different sizes of oil filters. This device should also be readily removable and reusable on different oil filters.